Conveners
Session 6: Application Oriented Research: Cathode Design
- Dave Dowell (Self)
We report on our recent advancements in development of a fully automated growth procedure for alkali antimonide photocathodes. Our goal is to create a capability that allows fabrication of uniform fully stoichiometric alkali antimonide films of any given thickness at sufficiently low substrate temperatures, where the compounds are stable. We show that co-evaporation procedure at low substrate...
We examine the potential of thin surface coatings to increase the QE of Nb while minimizing any additional RF losses. It is found that ultra-thin layers of Cs2Te on Nb, as low as 1.5 nm, still exhibit QE~6%. A phenomenological model of the Nb/Cs2Te bilayer is in good agreement with the measured thickness dependence. We also explore metal overlayers to exploit the superconducting proximity...
Interference enhanced, etalon photocathodes are promising due to the potential to enhance quantum efficiency without increasing emittance. This is likely so long as emittance is dominated by the excess energy (ħω-φeff) rather than being thermalization dependent, since the etalon effect does not directly change the band structure of the material. Enhancement occurs both by increasing absorption...
Photocathodes are important electron sources for X-ray free electron laser (XFEL) and X-ray energy recovery linacs (XERL), which generate brilliant, ultrafast, and coherent X-rays for exploration of matter with ultrahigh resolutions in both space and time. Quantum efficiency (QE) and operational lifetimes are two of the key figures of merit of photocathodes performance. Whereas alkali-based...
Alkali antimonide photocathodes have attractive properties, such as low-emittance and high quantum efficiency, which makes them excellent candidates for high-brightness electron sources. Less attractively, these materials are highly reactive and require ultra-high vacuum conditions to prevent irreversible oxidation, which precludes ex-situ characterization. Such limitations have stymied a...
